|PTHREAD_SETCONCURRENCY(3)||Linux Programmer's Manual||PTHREAD_SETCONCURRENCY(3)|
int pthread_setconcurrency(int new_level); int pthread_getconcurrency(void);
Compile and link with -pthread.
Specifying new_level as 0 instructs the implementation to manage the concurrency level as it deems appropriate.
pthread_getconcurrency() returns the current value of the concurrency level for this process.
pthread_getconcurrency() always succeeds, returning the concurrency level set by a previous call to pthread_setconcurrency(), or 0, if pthread_setconcurrency() has not previously been called.
- new_level is negative.
POSIX.1 also documents an EAGAIN error ("the value specified by new_level would cause a system resource to be exceeded").
|pthread_setconcurrency (), pthread_getconcurrency ()||Thread safety||MT-Safe|
Concurrency levels are meaningful only for M:N threading implementations, where at any moment a subset of a process's set of user-level threads may be bound to a smaller number of kernel-scheduling entities. Setting the concurrency level allows the application to give the system a hint as to the number of kernel-scheduling entities that should be provided for efficient execution of the application.
Both LinuxThreads and NPTL are 1:1 threading implementations, so setting the concurrency level has no meaning. In other words, on Linux these functions merely exist for compatibility with other systems, and they have no effect on the execution of a program.